1. Field of the Invention
The present invention relates to multiple spindle machining apparatus, and particularly to a type of multiple spindle drill which is adapted for drilling closely spaced holes in an economical and facile manner.
2. Description of the Prior Art
In the manufacture of certain types of electrical equipment, notably aircraft instruments, it is frequently necessary to drill small, closely spaced holes in the work.
In U.S. Pat. No. 2,342,251, Burt discloses multiple spindle drilling apparatus in which each drill bit extends through a face plate and a housing, and includes a crank at the internal extremity thereof, which crank is coupled to a drive plate, which is in turn, rotated by a main drive shaft. The arrangement disclosed by Burt employs an oiling system in which the drill splindles are oiled during operation. According to the teachings of Burt, the driver plate comprises a pair of sandwiched members, one of which has holes extending therethrough for engagement with the crank pins of all of the drive spindles.
In U.S. Pat. No. 3,606,559, Fitch, et al, teach a multiple spindle arrangement for a drilling machine, which likewise employs a crank pin arrangement like that disclosed by Burt. A similar crank pin arrangement is disclosed in U.S. Pat. No. 3,559,495 to Ludwig. Other prior art of interest includes U.S. Pat. No. 1,870,391 to Stimpson; and U.S. Pat. No. 3,682,560 To Suizu.
The machine structures illustrated in the prior art references discussed above serve a useful purpose where a particular drilling jig may be set up to drill thousands, or tens of thousands of a particular type of product. However, in low volume manufacturing jobs, such as those related to aircraft instruments of the type referred to above, it may be necessary to drill closely spaced, multiple holes in a particular type of work, but in which the spacing is the same only for a few hundred operations. Under these conditions, it is necessary to employ different structures and techniques than those taught in the above referenced patents, in order that the tooling costs do not render such multiple spindle drilling jigs unprofitable.